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rATE PLANT BOARD 

August 1952 E-843 



United States Department of Agriculture 

Agricultural Research Administration 

Bureau of Entomology and Plant Quarantine 



THE RELATIVE TOXICITY TO HOUSE FLIES OF ENDRIN AND 
ISODRIN IN KEROSENE SPRAYS 

By W. A. Gersdorff, Norman Mitlin, and R. H. Nelson 
Division of Insecticide Investigations 



Two compounds closely related to dieldrin and aldrin have recently 
shown promise as insecticides. They have been designated by the manu- 
facturer as compounds 269 and 711, but will be known hereafter as endrin 
and isodrin. 

Samples of these materials were obtained for preliminary evaluation 
of toxicity. Although of technical grade, they were crystalline. The 
sample of endrin was slightly brownish and that of isodrin white; the 
former was 84 percent and the latter 95 percent pure. They were not 
further purified. A purified sample of aldrin (m.p. 95 -98° C.) was used 
as a standard of comparison because of its close chemical relationship 
to these compounds. Pyrethrins, the common standard for space sprays, 
was also included in the study; it contained 52 percent of pyrethrin I and 
cinerin I. 

Procedure 

Stock solutions of the materials in refined kerosene were prepared. 
To insure a prompt and complete solution, acetone was used as an auxiliary 
solvent. It was particularly needed for the less soluble endrin. After 
preliminary tests, these stock solutions were further diluted with kerosene 
to form sprays containing four concentrations of each material that would 
give a range of mortalities of test insects to extend over the 50-percent 
point. The highest concentration of acetone in the sprays was 1.5 percent 
by volume. This concentration has not been found to have a measurable 
effect on the mortality caused by a number of materials tested by this 
method. 

The test insect was the house fly ( Musca domestica L.). Knockdown 
and mortality were determined by the Campbell turntable method. Eight 
replications were made, all sprays being tested in duplicate against each 
of four populations of flies; approximately 90 flies averaging 2 1/2 days in 
age were used in each test. 



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To evaluate relative toxicity and determine the precision of the 
estimates, the mortality data were subjected to probit analysis as 
described by Finney (1). 

Knockdown and Mortality 

Knockdown of flies was complete for the pyrethrins sprays, as is 
usual by this method at the concentrations used. All the other sprays 
caused no knockdown. The mortality data are summarized in table 1. 
They show that the samples of endrin and isodrin did not differ greatly 
in toxicity, if at all, and were substantially less toxic than aldrin but 
much more toxic than pyrethrins. 

Table 1. --Relative toxicity to house flies of endrin, isodrin, aldrin, 
and pyrethrins in kerosene sprays 



Material 



Concentration 



Mortality 
in 1 day 



LC-50 



Relative toxicity 





Mg. per dl. 


Percent 


Mg. per dl. 


Percent 


Endrin 


30.0 


78.8 


17.49+0.45 


67.2+2.6 




20.0 


57.4 








13.33 


32.1 








8.89 


18.4 






Isodrin 


30.0 
20.0 
13.33 
8.89 


74.3 
46.8 
29.5 
17.0 


19.31+0.51 


60.9+2.4 


Aldrin 


30.0 
20.0 
13.33 
8.89 


94.3 
78.5 
58,2 
29.9 


11.76+0.34 


100 


Pyrethrins 


800 
400 
200 
100 


87.8 
68.9 
31.2 
19.4 


265.2+21.7 


4.43+0.38 



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Evaluation of Relative Toxicity 

Analysis showed that, when probits were plotted against log concen- 
trations, the data for endrin, isodrin, and aldrin could be represented by 
parallel lines. Therefore, a generalization procedure as described by 
Finney (1) was used, the common regression coefficient being 3.35+0.12 
probits per unit log concentration. Since the slope of the line representing 
the data for pyrethrins was significantly different, the data for this mate- 
rial were not included in the generalization; the regression coefficient of 
the individually fitted line for pyrethrins was 2.36+0.32. Heterogeneity 
between populations of flies was great enough to result in significant 
chi-squares measuring departures from linearity for isodrin and 
pyrethrins. Therefore, all variances obtained in the determination 
of the precision of the estimates were multiplied by a heterogeneity 
factor; this factor for the pooled chlorinated hydrocarbons was 2.23 
and for pyrethrins 3.20. 

The statistically computed equations showing the regression of 
mortality, expressed in probits, on concentration in milligrams per 
deciliter, expressed as logarithms, are as follows: 

Endrin Y = 3.3506 X + 0.8360 

Isodrin Y = 3.3506 X + 0.6915 

Aldrin Y = 3.3506 X + 1 .4136 

Pyrethrins Y = 2.3636 X - 0.7282 

From these equations the median lethal concentrations (LC-50's) 
were calculated. Relative toxicity was then determined as the inverse 
ratios of LC-50's. These estimations and their standard errors are 
also given in table 1. 

Conclusions 

Statistical analysis showed the difference in the relative toxicities 
of endrin and isodrin to be significant. 

The sample of endrin was 67 percent as toxic as aldrin and, according 
to the ratio of the toxicity of aldrin to that of dieldrin (0.68) found previ- 
ously by this method (Gersdorff et al. 2), 46 percent as toxic as dieldrin. 

The sample of isodrin was 61 percent as toxic as aldrin. 

At the median lethal concentration the samples of endrin, isodrin, 
and aldrin were 15, 14, and 23 times as toxic as pyrethrins. The last 
ratio agrees very well with those obtained in two earlier comparisons 
of aldrin and pyrethrins by this method (Gersdorff et al. 2). 

Endrin, isodrin, and aldrin caused no knockdown at the concentra- 
tions used. 



UNIVERSITY OF FLORIDA 



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Literature Cited 



3 1262 09239 6398 



(1) Finney, D. J. 

1947. Probit analysis. 256 pp. Cambridge. 

(2) Gersdorff, W. A., Nelson, R. H., and Mitlin, Norman 

1950. The relative toxicity of heptachlor, aldrin, and dieldrin to 
house flies when applied as space sprays using Campbell 
turntable method. Soap and Sanit. Chem. 26(4): 137, 139